Non-impact type recording apparatuses represented by heat sensitive recording apparatuses are advantageous because they do not produce much noise, compared with impact type recording apparatuses, and therefore do not deteriorate the office work environment. In one transfer type heat sensitive recording apparatus, an ink image is transferred onto a recording paper by applying heat pulses to a heat transfer recording medium comprised of a base material having thereon an ink layer capable of heat transfer. Therefore, in comparison with conventional recording apparatuses utilizing recording paper of the heat sensitive coloration type, apparatuses of the above-described type have greater advantages in that (1) plain paper can be employed as recording paper, and (2) since an ink layer is made up of a mixture of binding agent like waxes, which can be fluidized or sublimed by applied heat, with a pigment or a dye, not only is the ink image obtained excellent in clarity and fastness, but the color of the image to be formed can be freely controlled by selecting proper pigments or dyes.
The heat transfer recording medium as a whole is shaped like carbon paper or carbon ribbon and utilizes tissue paper excellent in thermal resistance and smoothness as a base material, as described in U.S. Pat. Nos. 2,917,996, 3,453,648 and 3,596,055. Conventional transfer type heat sensitive recording apparatuses are constructed such that a heat transfer recording medium is wound on a roll and continuously supplied to its recording position (called a supplying roll hereinafter). When a heat transfer recording medium is allowed to stand for a long time in such a transfer type heat sensitive recording apparatus at high temperature and humidity conditions, the base material expands by absorbing moisture. This expansion phenomenon occurs to a large extent in the part paid out of the supplying roll toward the recording position in the transfer type heat sensitive recording apparatus. The degree of expansion which takes place is not uniform. The heat transfer recording medium can absorb a large amount of moisture and expand unrestrictedly only in the part which is paid out of the supplying roll and thereby, comes into contact with the atmosphere. However, expansion is hindered with respect to parts which are in contact with and pressed by conveying rollers and like attachments. If the heat transfer recording medium is expanded nonuniformly, it will make waves upwards and downwards in the medium. In practice the parts waving upwards and downwards are frequently converted to "puckers" when heated by a thermal head in the recording region. In the event that the puckers are produced in the heat transfer recording medium, transfer of ink onto recording paper in the recording region can not be effected with a good result, and an ink image obtained is partially missing, creating blank spots. Such a phenomenon is responsible for disadvantages such as decreasing the quality of the image obtained, and/or a failure to reproduce essential image information.